these circuits are the perfect example when to refrain from calling things 'ground' at all. 0V, common, return, even mass, everything is a lot less confusing and debatable.
Good content as always. I hope you decide to make a follow on video that covers the following related topics that are sometimes unclear:} 1. Proper fusing 2. Sometimes the primary ground wire is connected to the secondary side ground, sometimes the grounds are left isolated. Discuss the advantages and disadvantages of each approach. (isolated vs. non isolated) 3. Metal chassis ground for the two cases above in #2.
I had a number of dumb serial terminals back in the mid 80s that had a 5 ohm 10 watt resistor across ( in parallel) with the 7805 reg. both used to get hot but i did allow for over 2 amps of 'regulated' 5 volts at the given load.
I had brought up the Subject why 7805 and 7905 existed while ago. I think the conclusion you made at the end wasn't correct. You said you need 7805 and 7905. But i think you can get away with two 7805s as long as you reverse the input and ground of negative side. The ground does NOT have to be shared among all the components. Each component can have its own local positive and negative lines. It's up to you to connect positive or negative to ground. For 7905 the input is negative and ground is positive. That makes it easier to connect both 7805 and 7905 tabs together to chasis without any isolations. If you use a 7805 in negative side you have to isolate its tab and screw and reverse the input voltage.
I have an old Fluke 8050A DMM that I embedded a microprocessor and graphical LCD display into, to replace ancient failed 7-segment LCD in it. It's internal schematic shows a positive ground configuration for the old F8 microprocess in there. So my circuit goes with the flow and also floats along with the rest. During development, however, I had to think Really Hard about how to connect to the TTL serial port on my MCU to avoid "issues" with external views of earth grounds and the like. Fortunately, this could only be an issue if the DMM common was connected to anything, as it was at the internel (positive) ground potential. Testing of the DMM was restricted to batteries and other components isolated from everything else while my laptop was connected to the serial port. I could see how that approach made things "work" easier, it was just a bit off the beaten path. In the end, I have nice color graphical LCD display with large friendly digits on my old DMM so it was all successfully navigated.
The first half of this video explains very well how to deal with the ripple 🙂👍 The second half at 4:45 shows how to make very confusing circuits by using a 7805 for the negative supply and other nonsense 😬👎 The third half starting at 8:00 shows how to do it properly 🙂👍
Talking about conduction angle & peak current would add nothing useful or educational to the video. But for those interested all you have to do is sort comments by newest first & you will find it at the bottom! The problem is there no consistant formula used for conduction angle & peak current. Conduction angle will be relatative to how far above ground you are & the peak current applied. Peak current required will vary considerably depending on your capacitance & if you are using Half Wave or Full Wave, which could result in 50 Hurts, 60 Hurts, 100 Hurts or 120 Hurts.
@ 6:48 now be like me and connect the second bridge rectifier to the same secondary transformer winding of the firtst 7805. The bridge rectifier will sort this out, right? So I thought. Then things went Electroboom 😂
In your last example with the grounded center tap, could you just use a 7810 between the + and - rails? I mean, I guess it wouldn't be as stable, especially with an unbalanced load, but theoretically it could work.
I have a some encapsulated pcb-mount SMSP modules (+/-15 and +5V). Is there any reason I shouldn't use them in series willy-nilly to get more voltages like 30V or 20V?
Warning: The following is offered by a self-taught hobbyist who has immense gaps in his EE education and understanding. I welcome gentle correction and teaching. The term "Ground" causes a great deal of confusion. IMHO, the term should be standardized to something like "Return." The term "Ground" brings forth images of the solid mass beneath your feet, which can not be penetrated, meaning that you can not go lower than that. Additionally, IMHO, calling something a "Negative Voltage" is also confusing and should be standardized to something like "Lowest Voltage Range." As you have explained, the current is always flowing in only one direction referenced to the actual "Earth." Again, IMH(Uneducated)O, there is no such thing as "Ground"... Conventional current is always flowing from a higher value to a lower value. So, for your demonstration, there would be +10 volts, +5 volts and 0 volts. The use of so called Negative voltages brings forth the idea that the current is flowing in the reverse direction, which it does not and making for more confusion. Please be kind... Cheers.
I think you’re getting too caught up in semantics… ground and negative voltage are standard terminology used by all EEs and aren’t taken literally. It’s taught quite early on in any introduction to circuits that ground is the term used for the reference node where all single-ended voltages will be measured by their difference to. This is where the term “negative voltage” comes from because it refers to a voltage lower than the chosen ground. If a negative voltage were connected to ground, current would flow to the negative voltage because it is a lower value than ground. Also… I think it’s not humble to accuse someone else of having gaps in their knowledge when you yourself have admitted you’re uneducated in your own comment (you literally said “in my honest uneducated opinion”). Just something to think about, cheers.
@@NameWith15Letters Thank you for your gracious reply. I am aware that the terms are used in common EE speak and the operation of current flow by these terms. However, the semantics are exactly the point; they cause confusion that could be reduced by the use of better/standardized terms. That is all that I am suggesting. Also, I did not accuse anyone else of having gaps in their knowledge. I was describing myself... I am the self-taught hobbyist, who admits that he has gaps in his knowledge base and that his opinion comes without a formal EE education. Might the lack of a formal EE education give me a better/outsider perspective on determining that the semantics are confusing? Possibly. I read that others are of this opinion, as well. I genuinely appreciate that you took the time to reply and I will give further consideration to your points. It is folks like you that make the EE Community great. Thank you.
@@t1d100 I apologize! I misread and thought the self taught hobbyist you were talking about was the video creator. That was my mistake. As a working EE, I personally believe that the words used for terminology don’t matter since they are merely signs designating an underlying concept. While there certainly are some more poetic options for designation, uprooting the established tradition just creates even more confusion. The multiple different names for SPI protocol data pins are one example of a designation in flux (master/slave, MOSI/MISO, CIPO/COPI, etc.). I’ve had a moment at my job where the flipped relationship between MOSI/MISO and CIPO/COPI resulted in confusion. I think with these weird semantics it’s better to treat them as completely isolated words and not try to infer where they got their name in the first place. Thank you for being gracious with me, once I again I apologize for misreading your comment!
@@NameWith15Letters No apology needed; I realized that you just misread it. And, I also realized that you were trying to help and had taken time to do that... Which I appreciate. You make additional good points. By just discussing the topic, we have set in motion the beginnings of change. I choose to be optimistic and hope for that change to be for the better. Cheers!
Nothing wrong with ground and negative voltages, trying to call them something else is just moving away from the norm. How do you cope with impedances where the J operator is the square root of minius one.
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these circuits are the perfect example when to refrain from calling things 'ground' at all.
0V, common, return, even mass, everything is a lot less confusing and debatable.
The problem of using a 7805 for a negative supply is that the tab is now no longer ground and has to be insulated if using a heatsink.
But then, you'd still have -Vin on the heatsink if you used a 7905.
Good content as always. I hope you decide to make a follow on video that covers the following related topics that are sometimes unclear:}
1. Proper fusing
2. Sometimes the primary ground wire is connected to the secondary side ground, sometimes the grounds are left isolated. Discuss the advantages and disadvantages of each approach. (isolated vs. non isolated)
3. Metal chassis ground for the two cases above in #2.
I had a number of dumb serial terminals back in the mid 80s that had a 5 ohm 10 watt resistor across ( in parallel) with the 7805 reg. both used to get hot but i did allow for over 2 amps of 'regulated' 5 volts at the given load.
I had brought up the Subject why 7805 and 7905 existed while ago. I think the conclusion you made at the end wasn't correct. You said you need 7805 and 7905. But i think you can get away with two 7805s as long as you reverse the input and ground of negative side. The ground does NOT have to be shared among all the components. Each component can have its own local positive and negative lines. It's up to you to connect positive or negative to ground.
For 7905 the input is negative and ground is positive. That makes it easier to connect both 7805 and 7905 tabs together to chasis without any isolations. If you use a 7805 in negative side you have to isolate its tab and screw and reverse the input voltage.
I have an old Fluke 8050A DMM that I embedded a microprocessor and graphical LCD display into, to replace ancient failed 7-segment LCD in it. It's internal schematic shows a positive ground configuration for the old F8 microprocess in there. So my circuit goes with the flow and also floats along with the rest. During development, however, I had to think Really Hard about how to connect to the TTL serial port on my MCU to avoid "issues" with external views of earth grounds and the like. Fortunately, this could only be an issue if the DMM common was connected to anything, as it was at the internel (positive) ground potential. Testing of the DMM was restricted to batteries and other components isolated from everything else while my laptop was connected to the serial port.
I could see how that approach made things "work" easier, it was just a bit off the beaten path. In the end, I have nice color graphical LCD display with large friendly digits on my old DMM so it was all successfully navigated.
I hope the equipment being powered by your power supply _also_ doesn't mind which way round it's connected!
The first half of this video explains very well how to deal with the ripple 🙂👍
The second half at 4:45 shows how to make very confusing circuits by using a 7805 for the negative supply and other nonsense 😬👎
The third half starting at 8:00 shows how to do it properly 🙂👍
one could also talk about the conduction angle and peak current in the rectum finder.
but as always 👌
The rectum finder?
Talking about conduction angle & peak current would add nothing useful or educational to the video.
But for those interested all you have to do is sort comments by newest first & you will find it at the bottom!
The problem is there no consistant formula used for conduction angle & peak current. Conduction angle will be relatative to how far above ground you are & the peak current applied. Peak current required will vary considerably depending on your capacitance & if you are using Half Wave or Full Wave, which could result in 50 Hurts, 60 Hurts, 100 Hurts or 120 Hurts.
@@JustMe-dx5xl wow 'nothing useful or educational' - thanks for sharing
Rectum finder? Is that some p0rnhub feature?
@@JustMe-dx5xl Apparently peak current hurts a lot.
@ 6:48 now be like me and connect the second bridge rectifier to the same secondary transformer winding of the firtst 7805. The bridge rectifier will sort this out, right? So I thought. Then things went Electroboom 😂
In your last example with the grounded center tap, could you just use a 7810 between the + and - rails? I mean, I guess it wouldn't be as stable, especially with an unbalanced load, but theoretically it could work.
I have a some encapsulated pcb-mount SMSP modules (+/-15 and +5V). Is there any reason I shouldn't use them in series willy-nilly to get more voltages like 30V or 20V?
Warning: The following is offered by a self-taught hobbyist who has immense gaps in his EE education and understanding. I welcome gentle correction and teaching. The term "Ground" causes a great deal of confusion. IMHO, the term should be standardized to something like "Return." The term "Ground" brings forth images of the solid mass beneath your feet, which can not be penetrated, meaning that you can not go lower than that. Additionally, IMHO, calling something a "Negative Voltage" is also confusing and should be standardized to something like "Lowest Voltage Range." As you have explained, the current is always flowing in only one direction referenced to the actual "Earth." Again, IMH(Uneducated)O, there is no such thing as "Ground"... Conventional current is always flowing from a higher value to a lower value. So, for your demonstration, there would be +10 volts, +5 volts and 0 volts. The use of so called Negative voltages brings forth the idea that the current is flowing in the reverse direction, which it does not and making for more confusion. Please be kind... Cheers.
I think you’re getting too caught up in semantics… ground and negative voltage are standard terminology used by all EEs and aren’t taken literally. It’s taught quite early on in any introduction to circuits that ground is the term used for the reference node where all single-ended voltages will be measured by their difference to. This is where the term “negative voltage” comes from because it refers to a voltage lower than the chosen ground. If a negative voltage were connected to ground, current would flow to the negative voltage because it is a lower value than ground. Also… I think it’s not humble to accuse someone else of having gaps in their knowledge when you yourself have admitted you’re uneducated in your own comment (you literally said “in my honest uneducated opinion”). Just something to think about, cheers.
@@NameWith15Letters Thank you for your gracious reply. I am aware that the terms are used in common EE speak and the operation of current flow by these terms. However, the semantics are exactly the point; they cause confusion that could be reduced by the use of better/standardized terms. That is all that I am suggesting. Also, I did not accuse anyone else of having gaps in their knowledge. I was describing myself... I am the self-taught hobbyist, who admits that he has gaps in his knowledge base and that his opinion comes without a formal EE education. Might the lack of a formal EE education give me a better/outsider perspective on determining that the semantics are confusing? Possibly. I read that others are of this opinion, as well. I genuinely appreciate that you took the time to reply and I will give further consideration to your points. It is folks like you that make the EE Community great. Thank you.
@@t1d100 I apologize! I misread and thought the self taught hobbyist you were talking about was the video creator. That was my mistake. As a working EE, I personally believe that the words used for terminology don’t matter since they are merely signs designating an underlying concept. While there certainly are some more poetic options for designation, uprooting the established tradition just creates even more confusion. The multiple different names for SPI protocol data pins are one example of a designation in flux (master/slave, MOSI/MISO, CIPO/COPI, etc.). I’ve had a moment at my job where the flipped relationship between MOSI/MISO and CIPO/COPI resulted in confusion. I think with these weird semantics it’s better to treat them as completely isolated words and not try to infer where they got their name in the first place. Thank you for being gracious with me, once I again I apologize for misreading your comment!
@@NameWith15Letters No apology needed; I realized that you just misread it. And, I also realized that you were trying to help and had taken time to do that... Which I appreciate. You make additional good points. By just discussing the topic, we have set in motion the beginnings of change. I choose to be optimistic and hope for that change to be for the better. Cheers!
Nothing wrong with ground and negative voltages, trying to call them something else is just moving away from the norm. How do you cope with impedances where the J operator is the square root of minius one.